The form is extremely unclear. Some kind of documentation about what format the entries should be in would help (eg. project should apparently be the transwiki prefix for your home project - it needs to say that, I only worked it out by looking at other people's entries). I would fix it myself, but I haven't been able to work it all out...
Actually, everything is explained through an editintro (did you click on one of the links on [[Attendees/en]]?). It says it right there: "# Project: Your main project in Interwiki syntax. E.g. "en" if your main project is English Wikipedia. If your main project isn't Wikipedia, please use something like "de:wikt" (language code first). Note: This creates an interwiki link. Anything that isn't in the correct syntax will break the template. Leave blank if you do not have an account or do not wish to link to your user page."
Few users have trouble filling out the form, from time to time I go through all entries and fix broken ones.
Regards,
Church of emacs